1000= 1 dollar.
I made about 10 purchases last week only using points, Maybe about $80 bucks total. Online you can use as many as you want both surprise, and earned points. Bonus points act like earned points but expire sooner. In store it takes from what ever the cashier can figure out, most of the time they don't know how to apply your surprise points offers which are pretty much just coupons for so much off if you spend a certain amount. You also need to know your pin to spend more then $10 in points at the store in person.
To really earn points you have to take advantage of there points back offers so you have to pay attention to there spam e-mails, check there coupons on there website ect and spend some money out of pocket. If you buy something with only points you will not earn any new points from it. So if there offering something for sale and part of the deal is you get half or all the value back in points you have to spend some real money to get it. Some people have luck just spending a penny and using points for the rest.
Best bet if you have free time read about it on slick deals website, some of those people have thousands of dollars worth of points, but they have no problem doing pretty shady things.